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LearningExpress Editors Updated on Aug 12, 2011
These mechanical comprehension practice questions are based on the actual ASVAB. Take this quiz to see how you would do if you took the exam today and to determine your strengths and weaknesses as you plan your study schedule.
Time: 19 minutes
- A 250-pound weight is being lifted using the pulley system shown here. How much force is necessary to lift the weight?
- 50 pounds
- 100 pounds
- 125 pounds
- 250 pounds
- When a mercury thermometer is placed in hot liquid, mercury will travel up the thermometer to provide an accurate temperature reading. Why does mercury rise in a thermometer when it is exposed to heat?
- Heat causes mercury to expand.
- Mercury is repelled by heat.
- Heat causes mercury to contract.
- Air bubbles push mercury up the thermometer.
- In the diagram, Holly wants to lift a 120-pound block using a lever. If the block is 11 feet from the pivot point and Holly is 6 feet from the pivot point, how much force must she apply to lift the block?
- 220 pounds
- 66 pounds
- 120 pounds
- 720 pounds
- The vertical motion of a piston is transferred to rotational motion at the crank. Based on the figure, what description best describes the position and direction of the piston when the crank arm is pointing downward?
- far left and stationary
- in the center and moving to the left
- in the center and moving to the right
- far right and stationary
- Ian goes on a trail run and covers 12 miles in 1.5 hours. How fast was Ian running?
- 6 mph
- 8 mph
- 10 mph
- 18 mph
- A 300-pound block is being pulled up an incline by a pulley. The incline is 25 feet long and rises 10 feet. Neglecting friction, how much force is necessary to move the block up the incline?
- 120 pounds
- 250 pounds
- 300 pounds
- 35 pounds
- A force of 10 pounds is required to move a spring 8 inches. How far will the spring stretch under 15 pounds of force?
- 12 inches
- 14 inches
- 16 inches
- 18 inches
- If 18 full turns are required to move a nut 1.2 inches, how many threads per inch does the screw have?
- 10
- 12
- 15
- 20
- Using a lever, a man is able to lift a 120-pound load with only 40 pounds of force. What is the mechanical advantage of the lever?
- 3
- 20
- 80
- How much force is required to lift a 300-pound weight using the pulley system shown above?
- 75 pounds
- 100 pounds
- 150 pounds
- 900 pounds
- If gear 1 turns clockwise, which other gears, if any, will also turn clockwise?
- 2 only
- 3 only
- 2 and 4
- None
- When a submarine dives, it fills its ballast tanks with water, causing all the following EXCEPT
- the density of the submarine to increase.
- the buoyancy of the submarine to decrease.
- the weight of the submarine to increase.
- the volume of the submarine to increase.
- Pulley system A offers no mechanical advantage, whereas pulley system B has a mechanical advantage of 2. In pulley system A, if the rope is pulled 10 feet, the hook will rise 10 feet. How many feet of rope must be pulled to raise the hook in pulley system B by 10 feet?
- 5 feet
- 10 feet
- 15 feet
- 20 feet
- Three trucks are parked on an incline. Their centers of gravity are marked by dots. Which truck is most likely to tip over?
- truck A
- truck B
- truck C
- All trucks are stable.
- The cable supporting the arm of the crane is attached to the arm in four different positions. In which position is the cable strained the most?
- cable A
- cable B
- cable C
- cable D
- A steel block has a density of 0.3 pounds per cubic inch. Its dimensions are 2" × 2" × 5". What is the weight of the block?
- 6 pounds
- 10 pounds
- 20 pounds
- 27 pounds
- In the diagram, Talia wants to lift a 90-pound block using a lever. If the block is 10 feet from the pivot point and Talia is 8 feet beyond that, how much force must she apply to lift the block?
- 45 pounds
- 80 pounds
- 90 pounds
- 50 pounds
- Which material is best suited for building a raft?
- metal
- wood
- glass
- concrete
- A single-speed bicycle has a front chain ring with 48 teeth and a back gear with 12 teeth. If the bicycle is pedaled at 90 rpm, how fast will the rear wheel turn?
- 15 rpm
- 90 rpm
- 180 rpm
- 360 rpm
- Which of the following pulley systems offers the least mechanical advantage?
- A
- B
- C
- They all offer the same advantage.
- In the diagram, two blocks are balanced on either side of a lever. One block weighs 50 pounds and the other weighs 100 pounds. If the 50-pound block is 8 feet to the left of the pivot point, how far to the right of the pivot point is the 100 pound block?
- 2 feet
- 4 feet
- 8 feet
- 16 feet
- What is the mechanical advantage of the pulley system shown here?
- 1
- 2
- 3
- 4
- Which of the following is heaviest?
- 1 cubic foot of water
- 1 cubic foot of lead
- 1 cubic foot of wood
- 1 cubic foot of ice
- Pulley A has 2.5 times the circumference of pulley B. If pulley A rotates at 50 revolutions per minute (rpm), how fast must pulley B rotate?
- 20 rpm
- 50 rpm
- 125 rpm
- 250 rpm
- If gear 3 turns counterclockwise, which other gear(s), if any, will turn clockwise?
- 1 and 5
- 2 and 4
- All will turn clockwise.
- None will turn clockwise.
Answers
- c. A pulley system of this type has a mechanical advantage of 2. So, a 250-pound weight can be lifted with 250 pounds ÷ 2 = 125 pounds.
- a. The density of mercury is strongly temperature dependent. When placed in hot liquid, mercury expands by a known amount, forcing small amounts of liquid mercury up the thermometer.
- a. w_{1} × d_{1} = w_{2} × d_{2}. 120 pounds × 11 feet = w_{2} × 6 feet. Solving for w_{2} gives 220 pounds.
- c. The crank is moving counterclockwise, meaning that when it is pointing downward it is moving away from the piston (to the right). So, the piston will be in a central position. Since the crank is moving to the right, the piston will also be moving to the right.
- b. 12 miles ÷ 1.5 hours = 8 miles per hour.
- a. The mechanical advantage (MA) of a ramp is determined by the length of the ramp, l, divided by the height gained, h. In this case, MA = = 25 feet ÷ 10 feet = 2.5. The force required to pull a 300-pound block up a ramp is 300 pounds ÷ 2.5 = 120 pounds.
- a. The force constant of the spring is 10 pounds ÷ 8 inches = 1.25 pounds per inch. Using the equation, F = kx, we have 15 pounds = 1.25 pounds per inch × x. Solving for x gives 12 inches.
- c. If 18 turns move the nut 1.2 inches, there are 18 turns ÷ 1.2 inches = 15 threads per inch.
- b. Mechanical advantage = output force ÷ input force. Here, 40 pounds of force is input to lift a 120-pound load. The mechanical advantage is 120 ÷ 40 = 3.
- a. The mechanical advantage of this pulley system is 4. The force required to lift the 300-pound load is 300 pounds ÷ 4 = 75 pounds.
- b. Gear 1 turning clockwise will cause gears 2 and 4 to turn counterclockwise. Gear 3 will be the only other gear that turns clockwise.
- d. When a submarine fills its tanks with water it becomes heavier, which decreases its buoyancy and increases its density. The volume of the submarine remains unchanged through the entire process.
- d. Because pulley system B has a mechanical advantage of 2, the rope must be pulled twice as far as pulley system A to do the same amount of work: 2 × 10 feet = 20 feet.
- a. If a vertical line is drawn straight down from the center of gravity, only the line for truck A reaches the ground outside of the truck's tires. This makes the truck unstable.
- a. Cable A is attached to the arm closest to the crane. Therefore, it has the weakest mechanical advantage and so will be under the most strain to support the weight of the arm.
- a. The total volume of the block is 2 inches × 2 inches × 5 inches = 20 inches^{3}. Its density is 0.3 pounds per cubic inch, so its total weight must be 20 inches^{3} × 0.3 pounds per inch^{3} = 6 pounds.
- d. w_{1} × d_{1} = w_{2} × d_{2}. Talia is 18 feet away from the pivot point. 90 pounds × 8 feet = 10 feet × w_{2}. Solving for w_{2} gives 50 pounds.
- b. Wood is the best choice. All other objects are very dense and will quickly sink. Wood offers a lower density while still remaining strong enough to function as a raft.
- d. Each full turn of the pedals will turn the rear wheel 48 ÷ 12 = 4 revolutions. If the pedals are turning at 90 rpm, the rear wheel will move at 4 × 90 rpm = 360 rpm.
- c. Pulley systems A and B offer a mechanical advantage of 2, whereas pulley system C offers a mechanical advantage of 1. In A and B, the rope used to raise the weight moves 2 feet for every 1 foot the pulley is raised, whereas in C the rope used to raise the weight moves 1 foot for every foot the weight is raised.
- b. w_{1} × d_{1} = w_{2} × d_{2}. 50 pounds × 8 feet = 100 pounds × d_{2}. Solving for d_{2} gives 4 feet.
- b. In this pulley system, the weight of the load is shared over 2 cables and so the mechanical advantage is 2.
- b. Since all materials occupy the same volume, the material with the greatest density will be the heaviest. Lead is an extremely dense material and is much denser than all other options.
- c. Since pulley A is 2.5 times greater in diameter than pulley B, each revolution of A will lead to 2.5 revolutions of B. If A rotates at 50 rpm, then B will rotate at 50 rpm × 2.5 = 125 rpm.
- b. If gear 3 turns counterclockwise, it will lead to its neighboring gears (2 and 4) to turn clockwise.
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From ASVAB: Power Practice. Copyright © 2010 by LearningExpress, LLC. All Rights Reserved.